Java Socket UDP Program

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClient
{
	public static void main(String[] args) throws Exception
	{
		DatagramSocket datagramSocket = new DatagramSocket();

		String content = "hello world!";

		byte[] buffer = content.getBytes();

		InetAddress address = InetAddress.getByName("localhost");

		DatagramPacket packet = new DatagramPacket(buffer,buffer.length,address,5678);

		datagramSocket.send(packet);

		byte[] b = new byte[100];

		DatagramPacket packet2 = new DatagramPacket(b,100);

		datagramSocket.receive(packet2);

		byte[] b2 = packet2.getData();

		int l = packet2.getLength();

		String str = new String(b2,0,l);

		System.out.println("length of string : " + str);

		datagramSocket.close();
	}
}

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPServer
{

	public static void main(String[] args)throws Exception
	{
		DatagramSocket datagramSocket = new DatagramSocket(5678);

		byte[] buffer = new byte[100];

		DatagramPacket packet = new DatagramPacket(buffer,100);

		datagramSocket.receive(packet);

		byte[] data = packet.getData();

		int i = packet.getLength();

		String content = new String(data,0,i);

		System.out.println("content from client : " + content);

		int length = content.length();

		String strLength = String.valueOf(length);

		byte[] b = strLength.getBytes();

		InetAddress address = packet.getAddress();

		int port = packet.getPort();

		DatagramPacket packet2 = new DatagramPacket(b,b.length,address,port);

		System.out.println("length: " + new String(b,0,b.length));

		datagramSocket.send(packet2);

		datagramSocket.close();


	}

}